Danny Lyon doesn't want to talk about the Chicago Outlaws Motorcycle Club. The legendary documentary photographer won't say much about riding alongside Cal, Funny Sonny, Johnny, and the rest of the leather-clad gang in the 1960s, on an old Triumph cobbled together in a Hyde Park garage out of parts kept in coffee cans. He won't go into great detail about the photos he took with his trusty Nikon: Benny, leaning back in the saddle, a silhouette lit up from streetlights and neon signs at Grand and Division; Big Barbara, with eyes you could get lost in, staring into a jukebox; or Andy, drinking Hamm's longnecks off a pool table at the Stoplight bar in Cicero.

Lyon, now 72, doesn't want the gang in which he embedded himself sensationalized the way he feels "the straight press" of his day did with headlines such as "Cycle Hoods Watched by Cops 2 Years." Ever an iconoclast when it comes to the media, Lyon once wrote that his goal was to "create photographs that would be stronger, more truthful, and more powerful than LIFE magazine," so that "LIFE magazine would be destroyed." A 1966 Chicago Tribune article set the scene at the Cork—an Outlaws clubhouse in suburban Lyons that the cops sought to close—in strangely detached, almost anthropological terms: "As Cousin Joe told a brief history of the Cork, a tall, Beatle-haired waitress wearing a large 'I Like Sex' button served drinks to some of the pierced-eared outlaws who were 'cooling their pipes.' That means resting their 'wheels' or 'getting a drink.'"

Lyon doesn't feel the need to say much in part because he already said enough in The Bikeriders, a raw, compelling touchstone of New Journalism and Chicago counterculture history that documents four years spent with the Chicago Outlaws at races, runs, club meetings, loose social gatherings, and even a funeral. First published in 1968 and set for a long-overdue reissue by Aperture Press in June, the book reportedly served as inspiration for Easy Rider, with Lyon's black-and-white photos and candid interviews painting an unvarnished portrait of the fast, furious, and sometimes fatal biker lifestyle. In a shot of a member's scrapbook that shows a clip from a newspaper ad plugging the CBS 2 premiere of Marlon Brando in The Wild One, Lyon slyly points out the difference between the idealized vision of biker culture and the reality he believed he was capturing.

When Lyon began to conceive the project that would become The Bikeriders, he wrote seeking advice from Hunter S. Thompson, who spent a year with the Hell's Angels for his own book. (The two New Journalism figures never met, but their correspondence is reproduced in The Seventh Dog, a chronicle of Lyon's 50-year career released by Phaidon Press earlier this month.) Lyon didn't like the response he received from Thompson: "He advised me not to join the Outlaws and to wear a helmet," he says. "I joined the club and seldom wore a helmet."

Born in Brooklyn and raised in Queens, Lyon took an early interest in his father's scrapbooks and the work of Walker Evans. At age 11, he took his first photographs—of his pet turtle. He began studying history in 1959 at the University of Chicago, but spent much of his time in the darkroom at Ida Noyes Hall. In his first year at the U. of C., he met fellow freshman Frank Jenner, who rode a 350cc BSA and who introduced Lyon to the world of motorcycles. Jenner's smiling portrait would be the first image in The Bikeriders. It was the beginning of a tumultuous decade Lyon would intimately capture on film, a period that would see him rise from being an undergrad in Hyde Park to a Guggenheim fellow by 1969.

At the time he started The Bikeriders, Lyon had already established a commitment to the technique of immersion journalism pioneered by George Plimpton. In 1962, he left Chicago on a career-changing trip south to witness the civil rights movement. In short order, he became an official photographer for the Student Nonviolent Coordinating Committee and made friends with movement luminaries such as Julian Bond and John Lewis. When Lyon spent time in a Georgia lockup during his first week of shooting, he looked across the prison block and saw Martin Luther King Jr. occupying a nearby cell.

Shortly after his return to Chicago, Lyon began documenting the Outlaws, so named because they weren't recognized by the American Motorcycle Association. (The gang is still part of the "one-percenter club," a play off a supposed AMA claim that 99 percent of its members are law-abiding citizens.) Renting an apartment on the 5400 block of South Woodlawn, he began following the Outlaws across the city and on runs across the midwest, in an "attempt to record and glorify the life of the American bikerider." Shadowing the gang for four years beginning in 1963—he was a full-fledged member between '65 and '66—Lyon was restless, shooting numerous other projects, including more of the civil rights struggle and a photo study of Appalachian transplants in Uptown. "I rode my TR6 into the neighborhood in 1965," Lyon recalls, "and did all of the work on a single street, Clifton Street, half of which was later demolished." He handed out copies of the contact prints to the poor whites who were his subjects.

In a foreword to the reissue of The Bikeriders, Lyon writes that he once worried his exposé of the subculture would mean "the bikerider would perish on the coffee tables of America." But today Outlaws chapters in a dozen countries still boast more than 1,500 members, some of whom are living up to the notoriety implied by their gang's name. During raids in Illinois, Indiana, and Ohio in 2012, law enforcement arrested 42 Outlaws members for, among other things, money laundering, extortion, drug violations, witness tampering, and running an illegal gambling operation.

Lyon's unsentimental time capsule, meanwhile, seems as vibrant as ever. In Crossing the Ohio, Louisville, in which a single rider looks back over his shoulder as he roars across a bridge, the photographer portrays the effortless cool of the motorheads; a panorama of riders in a field of dandelions is a paean to the open road. Those shots are juxtaposed with photos of mud-splattered racers, family life, and the sobering images of pallbearers in leather jackets. The interviews—with members, other riders, wives, girlfriends—read the same way: off-the-cuff, alive with big, unruly personalities. Cal, a former army MP who got an undesirable discharge for arresting (and bad-mouthing) a commanding officer, gets philosophical about custom bikes: "They're all different. 'Cause everybody's melon's different. Everybody thinks different. So when I look at a chopper, man, I respect the dude because he made his." Frank Jenner recalls getting roughed up by cops; a woman named Kathy talks about her tumultuous relationship with the quick-tempered Benny; and Funny Sonny cracks up recounting a picnic with the Outlaws at Starved Rock, located 100 miles west of Chicago, where he and the others sped down dirt trails while hoisting jugs of wine.

In the course of his work, Lyon always sought counsel from Hugh Edwards, an influential curator at the Art Institute to whom Lyon dedicated The Bikeriders. A "friend and an intellectual father" to the photographer, according to a 1996 article in DoubleTake, Edwards met Lyon in 1959 during a U. of C. Festival of the Arts event. Lyon would roll up to the loading dock of the Art Institute, "four hundred pounds of machine under me, noisy and happy," to show him work in progress and get feedback about the project. The curator helped the photographer decide to extract himself from the gang and finish the years-long endeavor.

"Edwards's answer to the question 'When am I done?' was, 'Oh, I suppose when you have covered every aspect of it.' And I answered, 'Then I am done,'" Lyon says. "I was tired of drinking beer every Friday, which was the night of the meetings. I was [more of] a pothead."

The book's 1968 release helped propel Lyon's career, and led to projects that include a book documenting the demolition that made way for the original World Trade Center (The Destruction of Lower Manhattan), a study of prison inmates in Texas (Conversations With the Dead), and a travel journal about China (Deep Sea Diver). The Seventh Dog includes his recent coverage of the Occupy movement, which gave this self-described "60s guy" a jolt.

"I like rebels and think they are intrinsic to the survival of our democracy," says Lyon, who now splits his time between New Mexico and New York. "Who is going to take on the Koch brothers? Who is going to physically put their bodies on the line over the future of the planet?" Hearing Lyon talk about it, one can sense the energy that propelled him, more than a half century ago, to round the curved roads along the co-op apartments in Hyde Park astride his Triumph, searching for the next photo.